The present invention relates to a wind tunnel for measuring the aerodynamics of a vehicle and has particular applicability to measuring the aerodynamics of trucks and truck tractors.
Generally speaking, a wind tunnel used to test the aerodynamics of a vehicle includes a housing within which a vehicle to be tested is positioned. An air flow generator or mover such as a fan or blower is used to create an air stream that is directed through a contraction cone and a test section within which the vehicle is positioned. Air typically exits from the wind tunnel through a diffuser. In one known approach, six extremely large fans were positioned in a single common duct downstream of the diffuser for moving air through the test section. This common duct was connected to a single additional downstream diffuser. Wind tunnels may be of an open circuit design in which atmospheric design where air is drawn into the contraction cone and discharged from the diffuser back to atmosphere. Alternatively, wind tunnels may be designed to recirculate air in a loop or return flow configuration. A wind tunnel also includes instrumentation for measuring the desired information, such as the wind drag created by a vehicle.
It is common practice to include the entire vehicle in a wind tunnel during a test. In the case of tractor trailer combinations, one common approach is to include either the tractor alone or the entire tractor and towed trailer or shortened mock towed trailer with or without wheels in the wind tunnel. In this latter case, the wind tunnel must be large enough to receive the entire tractor trailer combination.
A need exists for a new and improved wind tunnel and associated methods for measuring the aerodynamics of vehicles, such as, but not limited to, tractors of the type which tow trailers.
In accordance with one embodiment, a wind tunnel for use in testing vehicles, such as cars, trucks, tractors, trains, airplanes and other vehicles, includes a housing with at least one air inlet and at least one air outlet. An air mover, which may comprise one or more blowers or fans, is coupled directly or indirectly to the housing and is adapted to create a flow of air through the housing in a direction from the air inlet toward the air outlet. The air mover may be downstream of the air outlet for drawing air through the housing or upstream of the air inlet for directing a flow of air into the housing.
A vehicle support is positioned at least partially within the housing for supporting a vehicle to be tested therein. The vehicle support is desirably operable to support the vehicle or the tires of the vehicle at an incline sloping from front to rear. Thus, in the case where entire vehicle is inclined, the vehicle is supported with its longitudal axis angled with respect to horizontal, and more specifically, angled upwardly from the rear toward the front of the vehicle. This would not typically be the case if only the tires of the vehicle are inclined.
A force measurer is coupled to the vehicle and is operable to measure the force resulting from the impingement or impact of moving air against the vehicle. Any suitable measuring device may be used, such as a conventional load cell positioned to engage a frame rail or other portion of the framework of the vehicle.
The incline at which the vehicle or vehicle tires may be supported may be adjustable. For wheeled vehicles, the angle is established at a magnitude which approximately compensates for the tire and bearing resistance of the vehicle so that more accurate measurements of the aerodynamics of the vehicle are obtained during the vehicle test. The inclined vehicle support, for example, may comprise any form of support which biases the vehicle in a desired direction, such as a bias which causes the wheels of the vehicle to roll backwardly in a front to rear direction. As a specific example, the vehicle support may comprise one or more inclined ramps positioned underneath the respective wheels of the vehicle. These ramps may take the form of plates which may be pivoted or otherwise adjustable to establish the desired incline. The plates may be manually adjustable or automatically adjustable such as in response to the operation of one or more hydraulic cylinders. The ramps may also be incorporated or built into the floor of the wind tunnel housing. Alternatively, the inclined support may be an inclined portion of the floor of the test section. The angle may be established at any desired magnitude. For example, a typical angle of incline ranges of from about one to about five degrees with two to three degrees incline from horizontal being more desirable typical angle. The angle is typically established to overcome and compensate for the static resistance to vehicle movement. The angle for each wheel is typically the same, although this is not necessary.
Air may exit from the housing of the wind tunnel through a plurality of ducts having duct inlets coupled directly to or indirectly to the air outlet of the housing. The air mover may comprise one or more fans coupled directly or indirectly to the air outlets for moving air through the housing. Desirably, a plurality of air movers are employed, each having a respective fan, for example. One such air mover and fan may be associated with and in communication with each of the respective ducts with the fan drawing air through the associated duct and from the housing or test section of the wind tunnel. The air movers typically include an air mover inlet and air mover outlet with an air flow generator such as fan positioned to draw air from the air mover inlet to the air mover outlet. The air mover inlets are coupled to the respective duct outlets of the air flow ducts which in turn are in communication with the air outlet of the housing. In a construction where the fans are isolated from one another by being coupled to separate ducts, interference between fans when they operate is minimized.
The wind tunnel also may comprise an air flow diffuser and more desirably a plurality of air flow diffusers. Each such diffuser may have a diffuser inlet in communication with, and coupled directly or indirectly to the air flow outlet of a respective one of the air flow generators. In one illustrated embodiment, there are at least ten of such air flow generators with associated ducts and diffusers. With this approach, relatively inexpensive HVAC fans may be used to moved the air through the test section.
The air flow ducts may be arranged in a generally horseshoe shaped or inverted U-shaped pattern at the air flow outlet end portion of the housing. A rear portion of the test vehicle may be positioned within this space with duct inlets being located along the sides and across the top of the vehicle. A pseudo-trailer may be coupled to the truck and surrounded along the sides and across the top by the duct inlets. The pseudo-trailer typically has no wheels and is of a length which terminates slightly rearwardly of the truck tractor to which the pseudo-trailer is coupled. The front of the pseudo-trailer has a foot print or a cross-sectional area which mimics the cross-sectional area of the front of a typical trailer to be towed by the truck tractor. The pseudo-trailer may also be configured to mimic the van or cargo portion of a truck and thus the term pseudo-trailer includes mock truck cargo portions of a vehicle. Although the wind tunnel may be expanded to accommodate full sized tractor-trailer combinations, a wind tunnel of reduced length may be used when pseudo-trailers are used in a vehicle test.
In one embodiment, the wind tunnel may comprise a conventional air contraction cone having an air contraction cone inlet through which air is drawn into the wind tunnel and a contraction cone outlet in communication with the air inlet end portion of the housing or test section of the wind tunnel. Although a recirculation system may be used, desirably the wind tunnel is an open system rather than one in which air is recycled.
The present invention is directed toward new and nonobvious features, method steps and acts as set forth herein both alone and in various subcombinations and combinations with one another.